Digital control calibration system for strip length gauge



Dec. 8,1970 s.|. DOYLE'IIIIETAL I I 3,54

DIGITAL CONTROL CALIBRATION SYSTEM FOR STRIP LENGTH GAUGE Filed July 8, 1969 2 Sheets-Sheeti 25 5 3w Lu l- 3% .J J g N :;5 .x? a.

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BRUCE I. DOYLE III CONSTANTINE VONTSOLOS United States Patent 3,545,087 DIGITAL CONTROL CALIBRATION SYSTEM FOR STRIP LENGTH GAUGE Bruce I. Doyle III, Roanoke, Va., and Constantine Vontsolos, Cincinnati, Ohio, assignors to General Electric Company, a corporation of New York Filed July 8, 1969, Ser. No. 839,838 Int. Cl. G01b 5/04 U.S. Cl. 33-132 4 Claims ABSTRACT OF THE DISCLOSURE An electrical system for calibrating a first counter which contains the algebraic sum of the output pulses of an entry tachometer and an exit tachometer representing the instant length of a metal strip passing through a wet looper pit. The algebraic sum, being in error due to slippage of the metal strip during exit from the looper pit, is periodically replaced by the contents of a memory list accumulated in a second counter during entry of the metal strip into the wet looper pit, this being the correct quantity due to lack of slippage of the strip at the entry end of the pit.

BACKGROUND OF THE INVENTION In steel mills where pickling lines are used for the removal of scale from the rolled coils of metal, the head end of one coil is welded to the tail end of the preceding coil, thereby forming a continuous strip of metal for processing by the pickle line. The pickle line is normally provided with a wet looper pit which contains enough metal strip material to allow the delay at the head end of the line for welding purposes without halting the motion of the tail end of the strip. The metal is introduced in the wet looper pit by a pair of pinch rolls. The exit pinch rolls withdraw the metal strip from the looper pit at a rate which is approximately equal to the average rate in which the strip is introduced so that the material within the looper pit fluctuates between a maximum and minimum set limit. The control of this range is normally performed by a pair of tachometers, one of which is located at the entry end of the pit and the other which is located at the exit end of the pit. These tachometers are driven by one of the rolls of the entry and one of the rolls at the exit side of the pit, each producing an output which is normally proportional to the length of the strip which is entering and leaving the looper pit, respectively. At the entry end of the looper pit, the strip is dry and the output signal is accurately proportional to the strip length passing between the pinch rolls, however at the exit end of the looper pit the strip is covered with a film of moisture from the looper pit and is subject to slipping between the rolls of the pinch roll, hence an output from the tachometer is not accurately proportional to the length of the metal strip leaving the looper pit. The error is accumulative and eventually becomes intolerable.

SUMMARY OF THE INVENTION To overcome this problem the present invention teaches a digital control calibrating system having an entry and an exit tachometer each of which is producing pulses in proportion to the length of several strips of material which enter and leave a looper pit. The strips are joined end to end and a punch press locates each joint by punching a hole therein as the strip material enters the looper pit. While punching a hole the punch press produces an electrical signal. A counter connected to both the entry and exit tachometers accumulates counts of which the number is equal to the difference between the outputs of the entry and exit tachometers. A second 'ice counter is connected to the entry tachometer and accumulates counts during the interval between signals from the punch press which also resets the second counter to zero. Several shift registers are provided for storing each of the accumulations of counts made by the second counter before that counter is reset to zero. A weld detector at the exit side of the looper pit detects a punched hole, denoting a joint between strips and produces an electrical signal which causes the contents of the first counter to be removed and replaced by the contents of the shift registers. Subsequent to this transfer the shift register containing the oldest accumulation by the second counter is reset to zero.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows the general layout of a wet looper pit.

FIG. 2 presents a block diagram showing the arrangement of components for performing the calibration functions of the system.

DESCRIPTION Referring now to FIG. 1 wherein the head end of an incoming metal strip 11, having been welded to the tail end of a preceding strip 12, is fed into a wet looper pit 25 by means of a pair of entry pinch rolls 27 and 29. Within the looper pit the head end of metal strip 12 is shown to be welded at point 18 to the tail end of metal strip 13 which in turn is welded at its head end at point 19 to the tail end of metal strip 14 which similarly is welded at its head end at point 20 to the tail end of strip 15, thus forming a continuous strip of metal passing through the wet looper pit 25. A pair of pinch rolls 21 and 23 withdraw the metal strip from the wet looper pit at the exit end, hence metal strip 15 is shown partially withdrawn therefrom. A punch press 39 at the entry side of the wet looper pit punches a hole at the 'weld locations 1720 for identification by the 'weld detector 35 located at the exit side of looper pit 25. An entry tachometer 31 driven by pinch roll 29 at the entry end of the wet looper pit produces pulses in proportion to the length of metal strip entering the looper pit through entry pinch rolls 27 and 29. An exit tachometer 33, driven by the pinch roll 23 at the exit end of the looper pit 25 produces electrical pulses in proportion to the length of strip being withdrawn from the looper pit. Referring now to FIGS. 1 and 2 wherein the output of the entry tachometer 31 and the exit tachometer 33 are applied to an asynchronous to synchronous logic circuit 41 which in the present art applies a resultant difference of pulses directly to a BCD (binary coded decimal) reversing counter 43 having the output thereof displayed in a digital display unit 45 representing the total amount of metal strip present in the wet looper pit 25. However, due to the metal strip, which is being withdrawn from looper pit 25, being wet, slippage very often occurs between the exit pinch rolls 21 and 23 and the metal strip; and as a consequence thereof, the exit tachometer 33 produces more pulses than representative metal strip passing between the rolls, hence a false indication of the amount of the metal strip present in the wet looper pit 25.

The present invention provides a calibrating system which periodically replaces the contents (the algebraic sum of pulses from the entry and exit tachometers 31 and 33, respectively) of the storage counter 43 by a count which is proportional to the length of metal strip which has passed into the looper pit 25 through the entry pinch rolls 27 and 29, since the last time the stored strip counter 43 was calibrated. The calibration is performed by applying the pulses produced by the entry tachometer 31, representing length of metal strip entering the looper pit through AND gate 47 which under certain conditions is enabled to allow these pulses to be applied to the incoming coil counter 49' of strip length list -1. A sequencing control 53 provides this enabling signal to a second input of AND gate 47 thereby permitting the binary incoming coil counter 49 to accumulate the pulses of the entry tachometer 31.

In addition to providing a punched hole in the metal strip, punch press 39 produces an electrical impulse each time a hole is punched, which is applied to the sequencing control 53. This causes the contents of shift register 55 to be shifted into shift register 56 and the contents of the incoming coil counter '53 to be shifted into shift register 55. The incoming coil counter 53 now accumulates the counts which are proportional to the length of strip 13. When the weld location 18 reaches punch press 39, a hole is again punched therein and the electrical signal produced by punch 39 is applied to the sequencing control 53 which causes the contents of shift register 56 to be shifted into shift register 57. The contents of shift register 55 is now moved into shift register 56 and the contents of the incoming coil counter is now moved into the shift register 55. The transfer of the contents of various shift registers 55-57 and the incoming coil counter 49 is performed simultaneously in a parallel fashion by a shift pulse applied thereto by sequencing control 53. The incoming coil counter 49 now accumulates pulses from the entry tachometer in proportion to the length of strip 12 which, when entirely accumulated causes the strip length list 51 to contain a number of pulses which represent the entire length of metal strips 12-14 accumulated in the looper pit 25. Recalibration takes place when the punched weld location 20 or in other words the head end of a coil is detected leaving the looper pit. At this instance, the strip length list which contains the exact length of strip in the pit is summed; i.e., the total contents of count in the incoming coil counter 49 and the shift registers 55-57 are added together. This sum or total is then placed in the stored strip counter 43- Where it replaces the algebraic sum which was obtained from the pulsed outputs of the exit and entry tachometers through the asynchronous to synchronous logic circuit 41. Therefore, any error introduced into the stored strip counter by the algebraic summing of the pulses of the entry and exit tachometers is erased as each coil leaves the wet looper pit.

The summing of the strip length list 51 is performed through the multiplex logic circuit 59. Sequencing control 53 causes the contents of the incoming coil counter 49 to be parallel transferred through Section A of the multiplex logic circuit 59 to the working counter 61. This working counter is a binary down counter which is preset by a quantity equal to the contents of the incoming coil counter 49. During the transfer of the contents of the incoming coil counter 49 to the working counter 61, the input of signals from the entry tachometer to the incoming coil counter are momentarily inhibited. In such case where a pulse occurred during the transfer period this pulse is temporarily stored in at capture bit, i.e., an extra bit in the incoming coil counter which will storage this one pulse while the contents of the rest of the incoming coil counter 49 is transferred. When the transfer is completed, the pulse is moved from. the capture bit into the counter and the capture bit is reset to zero. Clock counts or a pulse train derived from a pulse generator (not shown) are applied to a first input of AND gate 63 which upon receiving an enabling signal applied to its second input from sequencing control 53 applies the clock pulses to the working counter 61 which is a. binary count down counter, whereupon this counter begins to reduce its contents with every clock pulse input thereto. Simultaneously with this, clock pulses are applied to a gating and steering circuit 65 which upon receiving an enabling signal from the sequencing control 53 causes the clock pulses to be applied to the storage strip counter 43. The enabling signal derived from sequencing control 53 causes a momentary inhibition of the signal of the asynchronous to synchronous logic circuit 41 from being applied to the stored strip counter 43, so that the stored strip counter accumulates counts at a rate which is equal to that used to down count the working counter 61. When the contents of the working counter reaches zero, a zero detecting circuit 67 causes sequencing control 53 to inhibit clock pulses to the working counter 61 and the stored strip counter 43. The. stored strip counter now contains the number previously contained in the working counter. During the aforegoing transfer period, the pulses produced by the entry tachometer for application to the input of the working counter were inhibited. When the transfer of the contents of the incoming coil counter 49 has been completed, the inhibit signal is removed and pulses produced by the entry tachometer applied to AND gate 47 will be accumulated by the incoming coil counter 49, representing the metal strip entering the looper pit 25. The contents of shift register 55 are similarly transferred through the multiplex logic 59', Section B, into the working counter 61 which then is similarly down counted to zero from its total contents previously stored in the shift register 55. When the contents of the working counter 61 has reached zero, the zero detector circuit 67 applies through the sequencing control 53 an inhibit signal to AND gate 63 which will stop clock pulses from entering the working counter '61. Simultaneously with down counting the working counter 61, clock pulses are applied to the storage strip counter 43 through gating and steering circuit 65 which causes counter 43 to accumulate an identical number of pulses as are being down counted from the Working counter 6-1. When the zero detector circuit 67 detects a contents of zero counts in the working counter 61, it applies through the sequencing control 53 an inhibiting signal to gating and steering circuit 65 thereby preventing further clock pulses from being applied to the storage strip counter 43. This counter now contains the contents of the incoming coil counter 49 in addition to the contents of shift register 55. Similarly the contents of shift register 56 is applied through Section C of the multiplex logic 59 to the working counter 61, causing the storage strip counter 43 to accumulate an equivalent number of counts as were removed from working counter 61. The storage strip counter 43 now contains the number of pulses previously the contents of the incoming coil counter 49, shift registers 55 and 56. The contents of the shift register 57 is now similarly moved through Section -D of the multiplex logic 59 into the working counter 61. This counters contents is then reduced to zero, the zero detector 67 causes the clock pulses through the AND gate 63 to working counter 61 and the storage strip counter 43 to be inhibited. Storage strip counter 43 now contains the number of counts previously stored in the entire strip length list which represents the entire contents of the looper pit. The shift register 57 which represents the metal strip leaving the looper pit is then reset to zero, thereby providing space for the parallel transfer of the information stored in shift register 56 at such time when the next punch signal enters the sequencing control 53. The contents of the storage strip counter 43 is displayed in display 45 thereby giving an indication to the operator controlling the wet looper pit. A comparator 69 deriving an electrical signal proportional to the contents of the storage strip counter 43 compares this quantity with a minimum preset number which is derived from the operators control thereby determining the minimum allowable contents of the looper pit. If the contents of the storage strip counter 43 be less than the preset minimum, additional strip removal from the exit side of the looper pit is inhibited until such time when the contents thereof is greater than the preset minimum quantity.

When the looper pit is full, i.e., when the incoming coil counter 49 and three shift registers 55-57 are full, entry of additional strip is prevented through an AND circuit 71, which when receiving a full signal from each of the components of the strip length list 51, produces a signal which is applied to a relay (not shown) which controls the incoming material through pinch rolls 27 and 29.

While the invention has been explained and described with the aid of particular embodiments thereof, it will be understood that the invention is not limited thereby and that many modifications retaining and utilizing the spirit thereof without departing essentially therefrom will occur to those skilled in the art in applying the invention to specific operating environments and conditions. -It is therefore contemplated by the appended claims to cover all such modifications as fall within the scope and spirit of the invention.

What is claimed is:

1. A digital control calibrating system having an entry tachometer and an exit tachometer, each producing electrical pulses in proportion to the length of a plurality of joined material strips entering and leaving a storage pit, comprising:

(a) means for marking each joint between material strips before entering the storage pit, said marking means producing a first electrical signal each time a joint is marked,

(b) a first counter connected to said entry and exit tachometers for accumulating a count equal to the ditference between the outputs of the entry and exit tachometers,

(c) a second counter connected to the entry tachometer for accumulating a count during the interval between successive first electrical signals, said counter being reset to zero in response to said first electrical signal,

(d) means connected to said second counter for storing a predetermined number of counts,

(e) means positioned at the exit end of the storage pit responsive to the detection of said joint marking for producing a second electrical signal,

(f) means responsive to said second electrical signal for removing the count of said first counter and replacing said contents with the sum of the contents of said second counter and said storage means, and

(g) means for removing the oldest count in said storage means after the summing of the contents of said storage means and said second counter.

2. The invention claimed in claim 1 wherein said marking means is a punch press having an electrical contact for producing a signal each time the punch press is activated.

3. The invention claimed in claim 1 wherein said storing means comprises a predetermined number of shift registers connected to said second counter and each other in a manner to permit parallel transfer of the contents of said second counter to one of said shift registers and further parallel transfer of the contents of that and successive shift registers to another shift register in successive order.

4. The invention. claimed in claim 2 wherein the means positioned at the exit end of the storage pit is a photoelectric detector having a light source and photocell which produces an electrical signal when light from the light source passes through the hole punched in the strip material and strikes the photoelectric cell.

References Cited UNITED STATES PATENTS 2,869,241 1/1959 Witt 33-132UX 3,182,402 5/1965 Klager 33-132 3,411,216 11/1968 Evans 33l29 S. CLEMENT SWISHER, Primary Examiner US. Cl. X.R. 731 

